LEWISTON — It was a long day on the court for Waynflete’s Morgan Warner.

The No. 6 seed in the MPA girls’ singles tennis tournament needed three sets and three hours to win her Round of 16 match Saturday at Lewiston High School against No. 11 seed Lauren Bourque of Messalonskee, as she dropped the first set 4-6 before winning the next two, 6-3, 7-6 (0).

After a short break, she faced No. 3 seed Caitlin Cass of Lincoln Academy in the quarterfinals. Again, Warner fell behind early, losing the first set 3-6. But she battled back in windy conditions to win the next two sets, 6-3, 6-3.

“It was just staying consistent, and I got a lot of support (from friends and family), which helped,” Warner said.

Warner was one of four girls and four boys who moved on to the semifinals Monday morning at Bates College. She’ll be joined by defending champion and No. 1 seed Grace Campanella of Kennebunk/Wells, No. 2 Elene Imnaishvili of Bangor and No. 5 Regitze Jacobsen of Mt. Desert Island.

The boys’ final four is defending champ and No. 1 seed Nick Forester of Falmouth, No. 2 Dariy Vykhodtsev of Thornton Academy, No. 4 Thorne Kieffer of Waynflete and unseeded freshman Archie McDonough of Yarmouth.

Campanella and Forester each advanced quickly. Campanella won 6-0, 6-0 in both of her matches, and Forester lost only one game in quarterfinals against Wes Goodwin of Freeport after winning 6-0, 6-0 in the Round of 16.

Vykhodtsev, a senior, is in the semifinals for the third time after not playing for Thornton Academy last year. He won 6-0, 6-0 in the Round of 16, then earned a 6-4, 6-0 victory over Ben Adey of Waynflete in the quarterfinals.

“I just like the team aspect of it,” Vykhodtsev said of returning to high school tennis this year. “I like Thornton Academy and I like to play (for my school). It’s a fun experience overall.”

Kieffer defeated No. 5 Leif Boddie of Greely in the quarterfinals, 6-3, 6-4.

“Last year, I lost a three-setter in the quarters, (so) I had a whole year to think about losing that match,” Kieffer said. “I had time to process and work on my mental game, because I know tennis is really mental.”

Kieffer will face Forester in the semifinals, and McDonough takes on Vykhodtsev.

In the girls’ competition, Madelyn Dwyer of Maranacook recorded the first upset of the day – a 6-2, 6-4 win over Falmouth’s Meredith Kelley, the No. 4 seed.

“I learned a lot, I learned I can be mentally tough,” Dwyer said. “I never came into it knowing I can beat the four seed, so going into it not knowing anything about her, I just played my game and got as many balls back as I could.”

Dwyer lost 6-1, 6-4 in the quarterfinals to Jacobsen, an exchange student from Denmark.

“It was 40-40 every game; she did not give up. A big applause for her,” said Jacobsen, who next plays Campanella.

Imnaishvili, an exchange student from the country of Georgia, won both of her matches in straight sets. She defeated Anastasia Kapothanasis of Cheverus 6-2, 6-0 in the quarterfinals.